Cool roofs are effective solutions to counter the overheating of building roofs, inhabited spaces below and urban areas in which buildings are located thanks to their capability of reflecting solar radiation. Nonetheless, the relatively low surface temperatures that they induce can cause condensation of humidity and leave the surface wetted for large part of the day, thus promoting the growth of bacteria, algae and other biological fouling; this can cause a quick decay of the solar reflective performance. Biological growth is countered by surface treatments, which however may be toxic and forbidden in many countries and may also vanish quickly. It can also be countered by lowering the thermal emittance and thus decreasing heat transfer by infrared radiation to the sky and the consequent night undercooling, but this can decrease the performance of cool roofs. An alternative approach, which is analyzed in this work, is to embed in the first layer below the cool roof surface a phase change material (PCM) that absorbs heat during the daytime and then releases it in the nighttime. This can increase the minimum surface temperatures, thus reducing the occurrence humidity condensation and, with this, the biological growth. In this work, preliminary results on the coupling of a cool roof surface with a PCM sublayer are presented, being obtained by theoretical investigation on commercial materials and taking into account the time evolution pattern of the environmental conditions.
Aguilar JLC, Smith GB, Gentle AR, Chen D. Optimum integration of albedo, sub-roof R-value, and phase change material for cool roofs. In Proc. BS 2013: 13th Conference of the International Building Performance Simulation Association, Chambery, France; 2013; p. 1315-1321.
Akbari H, Bretz S, Kurn DM, Hanford J. Peak power and cooling energy savings of high-albedo roofs, Energy and Buildings 1997;25:117-126.
Akbari H, Bretz S. Long-term performance of high-albedo roof coatings. Energy and Buildings 1997;25:159-167.
Akbari H, Konopacki S, Pomerantz M. Cooling energy savings potential of reflective roofs for residential and commercial buildings in the United States, Energy 1999;24:391-407.
Akbari H, Menon S, Rosenfeld A. Global cooling: Increasing world-wide urban albedos to offset CO2, Climatic Change 2009;94:275-286.
AriÃ±o X, Gomez-Bolea A, Saiz-Jimenez C. Lichens on ancient mortar. International Biodeterioration and Biodegradation 1997;40:217-224.
Barozzi GS, Corticelli MA, Libbra A, Muscio A, Tartarini P. Building structures with high thermal inertia based on phase change materials. Int. J. of Heat and Technology 2009;27:121-126.
Berdahl P, Bretz SE. Preliminary survey of the solar reflectance of cool roofing materials. Energy and Buildings 1997;25:149-158.
Berdahl P, Akbari H, Rose LS. Aging of reflective roofs: soot deposition. Applied Optics 2002;41:2355-2360.
Berdahl P, Akbari H, Levinson R, Miller WA. Weathering of roofing materials â€“ An overview. Construction and Building Materials 2008;22:423-433.
Carbonari A, De Grassi M, Di Perna C, Principi P. Numerical and experimental analyses of PCM containing sandwich panels for prefabricated walls. Energy and Buildings 2006;38 472-483.
Characklis WG, Marshall KC. Biofilms. New York: Wiley; 1990.
Chou HM, Chen CR, Nguyen VL. A new design of metal-sheet cool roof using PCM. Energy and Buildings 2013;57:42-50.
Chung MH, Park JC. Development of PCM cool roof system to control urban heat island considering temperate climatic conditions. Energy and Buildings 2016;116:341-348.
CRRC â€“ Cool Roof Rating Council. RATED PRODUCTS DIRECTORY. Available from Internet: http://coolroofs.org/products/results, 2015.
Diamanti MV, Paolini R, Zinzi M, Ormellese M, Fiori M, Pedeferri MP. Self-cleaning ability and cooling effect of TiO2-containing mortars. In: Technical Proc. of the NSTI-Nanotech 2013 â€“ 2013 NSTI Nanotechnology Conference and Expo. Washington, DC; 2013; vol. 3, p. 716-719.
DuPont. Energain Data Sheet â€“ Measured Properties. Retrieved on http://energain.co.uk/Energain/en_GB/assets/downloads/documentation/download/Energain%C2%AE_Datasheet_UK.pdf, in 2016.
ECRC â€“ European Cool Roof Council. Product Rating Database. Available from Internet: http://coolroofcouncil.eu/rpd.php, 2015.
Farid MM, Khudhair AM, Razack SAK, Al-Hallaj S. A review on phase change energy storage: materials and applications. Energy Conversion and Management 2004;45:1597-1615.
Ferrari C, Santunione G, Libbra A, Muscio A, Sgarbi E, Siligardi C, Barozzi GS. Review On The Influence Of Biological Deterioration On The Surface Properties Of Building Materials: Organisms, Materials, And Methods. Int. J. of Design & Nature and Ecodynamics 2015;10:21-39.
Gaylarde C, Morton LHG. Biodeterioration of mineral materials. In: Enc. of Environmental Microbiology, New York: Wiley, 2002; p. 515-528.
Gaylarde CC, Gaylarde PM. A comparative study of the major microbial biomass of biofilms on exteriors of buildings in Europe and Latin America. International Biodeterioration and Biodegradation 2005;55:131-139.
Ichinose M, Inoue T, Sakamoto Y. Long-term performance of high-reflectivity exterior panels. Building and Environment 2009;44:1601-1608.
ISO â€“ International Organization for Standardization. ISO 6946:2007 â€“ Building components and building elements â€“ Thermal resistance and thermal transmittance â€“ Calculation method. 2007a.
ISO â€“ International Organization for Standardization. ISO 13786:2007 â€“ Thermal performance of building components â€“ Dynamic Thermal characteristics â€“ Calculation Methods. 2007b.
John DM. Algal growth on buildings: a general review and methods of treatment. Biodeterioration Abstracts 1998;2:81-102.
Karlessi T, Santamouris M, Synnefa A, Assimakopoulos D, Didaskalopoulos P, Apostolakis K. Development and testing of PCM doped coolcolored coatings to mitigate urban heat island and cool buildings. Build. Environ. 2011;46:570-576.
Khudhair AM, Farid MM. A review on energy conservation in building applications with thermal storage by latent heat using phase change materials. Energy Conversion and Management 2004;45:263-275.
Le DÃ» M, Zalewski L, Lassue S, Dutil Y, Rousse D. Thermophysical characterization of a composite phase change material: the specific case of EnergainÂ®. Proc. of the 12th International Conference on Energy Storage; 2012.
Levinson R, Akbari H, Konopacki S, Bretz S. Inclusion of cool roofs in nonresidential Title 24 prescriptive requirements, Energy Policy 2005;33:151-170.
Magli S, Lodi C, Contini FM, Muscio A, Tartarini P. Dynamic analysis of the heat released by tertiary buildings and the effects of urban heat island mitigation strategies, Energy and Buildings 2016;114:164-172.
Mastrapostoli E, Santamouris M, Kolokotsa D, Vassilis P, Venieri D, Gompakis K. On the ageing of cool roofs: Measure of the optical degradation,chemical and biological analysis and assessment of the energy impact. Energy and Buildings 2016;114:191-199.
Mavrigiannaki A, Ampatzi E. Latent heat storage in building elements: A systematic review on properties and contextual performance factors. Renewable and Sustainable Energy Reviews 2016;60:852-866.
Paolini R, Zinzi M, Poli T, Carnielo E, Mainini AG. Effect of ageing on solar spectral reflectance of roofing membranes: Natural exposure in Roma and Milano and the impact on the energy needs of commercial buildings. Energy and Buildings 2014;84:333-343.
Pisello AL, Fortunati E, Mattioli S, Cabeza LF, Barreneche C, Kenny JM, Cotana F. Innovative cool roofing membrane with integrated phase changematerials: Experimental characterization of morphological, thermal and optic-energy behavior. Energy and Buildings 2016;112:40-48.
Roman KK, O'Brien T, Alvey B, Woo O. Simulating the effects of cool roof and PCM (phase change materials) based roof to mitigate UHI (urban heat island) in prominent US cities. Energy 2016;96:103-117.
Rosenfeld AH, Akbari H, Bretz S, Fishman BL, Kurn DM, Sailor D, Taha H. Mitigation of urban heat islands: materials, utility programs, updates. Energy and Buildings 1995;22:255-265.
Rosenfeld AH, Akbari H, Romm JJ, Pomerantz M. Cool communities: Strategies for heat island mitigation and smog reduction, Energy and Buildings 1998;28:51-62.
Schossig P, Henning H-M, Gschwander S, Haussmann T. Micro-encapsulatedphase-change materials integrated into construction materials. Solar Energy Materials & Solar Cells, 2005;89:297-306.
Sleiman M, Ban-Weiss G, Gilbert HE, FranÃ§ois D, Berdahl P, Kirchstetter TW, Destaillats H, Levinson R. Soiling of building envelope surfaces and its effect on solar reflectance â€“ Part I: Analysis of roofing product databases. Solar Energy Materials and Solar Cells 2011; 95:3385-3399.
Sleiman M, Kirchstetter TW, Berdahl P, Gilbert HE, Quelen S, Marlot L, Preble CV, Chen S, Montalbano A, Rosseler O, Akbari H, Levinson R, Destaillats H. Soiling of building envelope surfaces and its effect on solar reflectance â€“ Part II: Development of an accelerated aging method for roofing materials. Solar Energy Materials and Solar Cells 2014;122:271-281.
Synnefa A, Santamouris M. Advances on technical, policy and market aspects of cool roof technology in Europe: The Cool Roofs project, Energy and Buildings 2012;55:35-41.
Synnefa A, Santamouris M, Livada I. A study of the thermal performance of reflective coatings for the urban environment, Solar Energy 2006;80:968-981.
Synnefa A, Santamouris M, Akbari H. Estimating the effect of using cool coatings on energy loads and thermal comfort in residential buildings in various climatic conditions, Energy and Buildings 2007;39:1167-1174.
Taha H, Akbari H, Rosenfeld AH, Huang J. Residential cooling loads and the urban heat island-the effects of albedo. Building and Environment 1989;23:271-283.
Tomaselli L, Lamenti G, Bosco M, Tiano P. Biodiversity of photosynthetic micro-organisms dwelling on stone monuments. International Biodeterioration and Biodegradation 2000;46:251-258.
Touchaei AG, Akbari H. The climate effects of increasing the albedo of roofs in a cold region, Advances in Building Energy Research 2013;7:186-191.
Tran TH, Govin A, Guyonnet R, Grosseau P, Lors C, Garcia-Diaz E, Damidot D, DevÃ¨s O, Ruot B. Influence of the intrinsic characteristics of mortars on their biofouling by pigmented organisms: Comparison between laboratory and field scale experiments. International Biodeterioration and Biodegradation 2014;86(Part C):334-342.
Tyagi VV, Buddhi D. PCM thermal storage in buildings: a state of art. Renewable and Sustainable Energy Reviews 2007;11:1146-1166.
US EPA â€“ U.S. Environmental Protection Agency. ENERGY STAR Certified Roof Products. Available from Internet: http://www.energystar.gov/productfinder/product/certified-roof-products, 2015.
Wee YC, Lee KB, Proliferation of algae on surfaces of buildings in Singapore. International Biodeterioration Bulletin 1980;16:113-117.
Zalba B, Marin JM, Cabeza LF, Mehling H. Review on thermal energy storage with phase change: materials, heat transfer analysis and applications. Applied Thermal Engineering 2003;23:251-283.
Zinzi M. Cool materials and cool roofs: potentialities in Mediterranean buildings, Advances in Building Energy Research 2010;4:201-266.